Capitalismo e direitos humanos de solidariedade: elementos para uma crítica

Nosso estudo busca identificar a conexão material entre o capitalismo e os direitos humanos de solidariedade. Esses direitos, segundo a teoria jurídica e as declarações internacionais, ao contemplarem toda a humanidade, ao conceberem o gênero humano como sujeito de direito, são a mais elevada expressão do progresso da consciência humana no que concerne a dignidade do homem e as ameaças contra a vida coletiva na Terra. Nós propomos, ao contrário, que os direitos humanos de terceira geração exprimem as formas mais abstratas do capitalismo depois da Segunda Guerra Mundial, especialmente aquelas que correspondem à finança e à mundialização do capital. A sociedade burguesa internacionalizada tornou-se ela mesma, em suas categorias fundamentais, mais abstrata, e as categorias jurídicas seguiram este mesmo movimento. E de modo similar ao que sucede com os direitos humanos de primeira geração e de segunda geração, as palavras charmosas apresentadas pelo humanismo jurídico portam, discretamente, a exploração capitalista. Os direitos ao patrimônio comum da humanidade, ao meio ambiente sadio, ao desenvolvimento e mesmo o direito à paz, cada um deles reproduz os meios de apropriação e organização capitalista do imperialismo os mesmos meios que dão suporte aos lucros privados sobre os bens coletivos, que mantêm a dominação imperialista e que preparam as guerras no interior do sistema de Estados. O idealismo e a visão romântica sobre os direitos humanos escondem esta contradição, e é preciso expô-la, é preciso superar a ideologia jurídica. Nossa crítica marxista, realizada pela crítica do capital e de sua forma jurídica em escala internacional, é um esforço nesta direção.

Collective effects in light scattering from cold strontium clouds

A cold atomic cloud is a versatile object, because it offers many handles to control and tune its properties. This facilitates studies of its behavior in various circumstances, such as sample temperature, size and density, composition, dimensionality and coherence time. The range of possible experiments is constrained by the specifications of the atomic species used. In this thesis presents the work done in the experiment for laser cooling of strontium atoms, focusing on its stability, which should provide cold and ultracold samples for the study of collective effects in light scattering. From the initial apparatus, innumerous changes were performed. The vacuum system got improved and now reached lower ultra high vacuum due to the pre-baking done to its parts and adding a titanium-sublimation stage. The quadrupole trap were improved by the design and construction of a new pair of coils. The stability of the blue, green and red laser systems and the loss prevention of laser light were improved, giving rise to a robust apparatus. Another important point is the development of homemade devices to reduce the costs and to be used as a monitor of different parts of an cold atoms experiment. From this homemade devices, we could demonstrate a dramatic linewidth narrowing by injection lock of an low cost 461 nm diode laser and its application to our strontium experiment. In the end, this improved experimental apparatus made possible the study of a new scattering effect, the mirror assisted coherent back-scattering (mCBS).

Excitations in Bose-Einstein condensates: collective modes, quantum turbulence and matter wave statistics

In this thesis, we present the generation and studies of a 87Rb Bose-Einstein condensate (BEC) perturbed by an oscillatory excitation. The atoms are trapped in a harmonic magnetic trap where, after an evaporative cooling process, we produce the BEC. In order to study the effect caused by oscillatory excitations, a quadrupole magnetic field time oscillatory is superimposed to the trapping potential. Through this perturbation, collective modes were observed. The dipole mode is excited even for low excitation amplitudes. However, a minimum excitation energy is needed to excite the condensate quadrupole mode. Observing the excited cloud in TOF expansion, we note that for excitation amplitude in which the quadrupole mode is excited, the cloud expands without invert its aspect ratio. By looking these clouds, after long time-of-flight, it was possible to see vortices and, sometimes, a turbulent state in the condensed cloud. We calculated the momentum distribution of the perturbed BECs and a power law behavior, like the law to Kolmogorov turbulence, was observed. Furthermore, we show that using the method that we have developed to calculate the momentum distribution, the distribution curve (including the power law exponent) exhibits a dependence on the quadrupole mode oscillation of the cloud. The randomness distribution of peaks and depletions in density distribution image of an expanded turbulent BEC, remind us to the intensity profile of a speckle light beam. The analogy between matter-wave speckle and light speckle is justified by showing the similarities in the spatial propagation (or time expansion) of the waves. In addition, the second order correlation function is evaluated and the same dependence with distance was observed for the both waves. This creates the possibility to understand the properties of quantum matter in a disordered state. The propagation of a three-dimensional speckle field (as the matter-wave speckle described here) creates an opportunity to investigate the speckle phenomenon existing in dimensions higher than 2D (the case of light speckle).